1. Field of the Invention
The present invention relates to a correction arithmetic circuit that utilizes a lookup table having stored therein correction data corresponding to input data at predetermined intervals relevant to predetermined higher-order bits.
2. Description of the Related Art
Conventionally, the gamma correction is executed based on gamma curves when video signals are displayed. The correction using gamma curves utilizes a lookup table. When a lookup table is utilized, a required memory capacity becomes very large if all the correction data corresponding to input data are stored. Therefore, the lookup table has stored therein the correction data for the input data at predetermined intervals. Although the correction data may be read and output if the correction data for the input are saved, the data must be saved and interpolation arithmetic must be executed to acquire video data after the gamma correction if the data are not stored.
Therefore, two adjacent correction data must be output for one item of input data from the lookup table. As a result, two addresses are generated and adjacent correction data are output for one item of input data. For example, it is assumed that input data have eight bits and that correction data corresponding to the high five bits of the input data are stored in the lookup table. In this case, two addresses are generated, which are an address 1 corresponding to the high five bits of the input data and an address 2 corresponding to a value of the high five bits +1, and correction data of these two addresses are output from the lookup table.
Therefore, a two-port memory is utilized as the lookup table to acquire two output data by concurrently specifying two addresses.
Related arts include Japanese Patent Application Laid-Open Publication No. 2005-323137.
However, since a two-port memory needs a circuit for concurrent access, it is problematic that an area of the lookup table is increased.